Click
here to close Hello! We notice that
you are using Internet Explorer, which is not supported by Echinobase
and may cause the site to display incorrectly. We suggest using a
current version of Chrome,
FireFox,
or Safari.
Cretac Res
2014 Mar 01;48:235-249. doi: 10.1016/j.cretres.2013.11.013.
Show Gene links
Show Anatomy links
Absurdaster, a new genus of basal atelostomate from the Early Cretaceous of Europe and its phylogenetic position.
Kroh A
,
Lukeneder A
,
Gallemí J
.
???displayArticle.abstract???
Field work in the Lower Cretaceous of the Dolomites (Italy) has resulted in the recovery of a new genus of 'disasteroid' echinoid, which successively was also discovered in slightly older strata in Northern Hungary. This new genus, Absurdaster, is characterized by its highly modified, disjunct apical disc in which all genital plate except genital plate 2 are reduced or fused. The gonopores (which may be multiple) have shifted and pierce interambulacral plates. Anteriorly ambulacrum III is distinctly sunken and forms a distinct frontal notch, while the posterior end is pointed and features a small sharply defined posterior face bearing the periproct. Two new species are established: Absurdaster puezensis sp. nov. from the Upper Hauterivian to Lower Barremian Puez Formation of Northern Italy is characterized by its rudimentary ambulacral pores in the paired ambulacra, high hexagonal ambulacral plates aborally and multiple gonopores in the most adapical plates of interambulacral columns 1b and 4a. Absurdaster hungaricus sp. nov. from the Lower Hauterivian Bersek Marl Formation of Northern Hungary, in contrast, shows circumflexed ambulacral pores, low ambulacral plates, a single gonopore each in the most adapical plates of interambulacral columns 1b and 4a and a flaring posterior end, with sharp margin and invaginated periproct. In addition to those two species Collyrites meriani Ooster, 1865 from the uppermost Berriasian to basal Barremian of Switzerland is attributed to the new genus. Despite the poor knowledge on this form it seems to be distinguished from the new species by its smaller ambulacral plates and higher interambulacral/ambulacral plate ratio. Phylogenetic analyses based on previous work by Barras (2007) and Saucède et al. (2007) indicate that the new genus is a highly derived stem-group member of the Atelostomata close to the split of holasteroids and spatangoids. A combined analysis based on a subset of the characters employed in these two studies for the first time results in a fully resolved tree for 'disasteroids'. Absurdaster, shows two notable morphological peculiarities: 1) it is one of the first echinoids to develop fascioles and exhibits a yet unknown type of fasciole circling the periproct, termed circumanal fasciole here; 2) it is extraordinary among echinoderms as its extraxial skeleton is reduced to a single plate, the madreporite (genital plate 2), and because its genital pores pierce axial elements rather than extraxial ones.
Fig. 4. Absurdaster puezensis sp. nov.: camera lucida drawings. 1: Holotype STMN PZO 341 (aboral view); 2: Paratype MG P-257 (oral view); 3: NHMW 2011/0387/0007 (aboral view); 4: Paratype NHMW 2011/0415/0001 (A: aboral view; B: apical disc); 5: Paratype NHMW 2011/0385/0003 (aboral view); 6: Paratype NHMW 2011/0405/0007, (A: aboral view; B: trivium). Interambulacra shaded in light grey, complemental plates in dark grey; uncertain sutures stippled. Numbering of the plate columns according to Lovén's system is indicated in grey font.
Fig. 5. Comparison of Absurdaster ambulacral plating. 1, 2: A. puezensis sp. nov.; 3, 4: A. hungaricus sp. nov. (1, 3: supraambital ambulacrum III, 2, 4: supraambital ambulacrum IV; 1: Paratype NHMW 2011/0397/0001, 2: Paratype NHMW 2011/0385/0003, 3: Holotype HNHM PAL 2013.30.1., 4: Paratype HNHM PAL 2013.32.1.). Interambulacra shaded.
Fig. 6. Comparison of Absurdaster ambulacral pores. 1, 2: A. puezensis sp. nov., whitened with ammonium chloride; 3, 4: A. hungaricus sp. nov., immersed in water; A: overview, B: detail of A. (1, 3: supraambital ambulacrum III, 2, 4: adapical ambulacrum IV; 1, 2: Paratype NHMW 2011/0405/0007, 3: Holotype HNHM PAL 2013.30.1., 4: Paratype HNHM PAL 2013.32.1.). Scale bars equal 1 mm.
Fig. 7. Absurdaster hungaricus sp. nov.: 1: Holotype HNHM PAL 2013.30.1. (A: aboral, B: oral, and C: right lateral view); 2: Paratype HNHM PAL 2013.31.1. (oral view); 3: Paratype HNHM PAL 2013.32.1. (A: aboral, B: oral, and C: left lateral view); 4: Paratype HNHM PAL 2013.33.1. (A: right lateral view of distorted test; B: posterior face). All specimens whitened with ammonium chloride.
Fig. 8. Absurdaster hungaricus sp. nov.: camera lucida drawings. 1: Holotype HNHM PAL 2013.30.1. (A: aboral view, B: apical disc detail); 2: Paratype HNHM PAL 2013.31.1. (oral view); 3: Paratype HNHM PAL 2013.32.1. (oral view). Lines marked by question marks in 2 are interpreted as fractures rather than sutures here. Interambulacra shaded; areas covered by sediment hatched. Numbering of the plate columns according to Lovén's system is indicated in grey font.
Fig. 9. Absurdaster hungaricus sp. nov.: Posterior face with invaginated periproct in paratype HNHM PAL 2013.33.1. (A: outside view of posterior face, B: vertical section, C: horizontal section viewed from above). Interambulacra shaded.
Fig. 11. Results of the phylogenetic analyses: A: 50%-majority-rule consensus tree of the analysis based on the matrix of Saucède et al. (2007), which indicates that Absurdaster is a stem-group members of the Atelostomata; B: 50% majority-rule consensus tree using Barras' (2007) matrix, which places Absurdaster within stem-group holasteroids, albeit with low support. Numbers above branches indicate bootstrap values above 50%, those below indicate Bremer indices above 1 (all other nodes collapse one step away from the shortest tree) respectively the percentage of trees that include the respective node for nodes that are not fully supported in the full set of MPTs.
Fig. 12. Results of the phylogenetic analyses based on the revised matrix: single most parsimonious tree. Conventions as for Fig. 11.
Lukeneder,
New biostratigraphic data on an Upper Hauterivian-Upper Barremian ammonite assemblage from the Dolomites (Southern Alps, Italy).
2012, Pubmed
Lukeneder,
New biostratigraphic data on an Upper Hauterivian-Upper Barremian ammonite assemblage from the Dolomites (Southern Alps, Italy).
2012,
Pubmed
Lukeneder,
The late Barremian Halimedides horizon of the Dolomites (Southern Alps, Italy).
2012,
Pubmed
Smith,
Large-scale heterogeneity of the fossil record: implications for Phanerozoic biodiversity studies.
2001,
Pubmed
Smith,
The geological history of deep-sea colonization by echinoids: roles of surface productivity and deep-water ventilation.
2005,
Pubmed
,
Echinobase
Stöver,
TreeGraph 2: combining and visualizing evidence from different phylogenetic analyses.
2010,
Pubmed